Shoppers are expected to go on a £2.5bn spending spree in the next 24 hours as Black Friday discount fever sweeps UK high streets. Friday promises to be a nail biting one for retailers who see the US inspired discount day as a litmus test ahead of the key Christmas trading period.

The high-street clothing bellwether Next, which traditionally refuses to offer pre-Christmas discounts, is entering the Black Friday fray for the first time to boost flagging sales amid a blizzard of promotions from rivals, including John Lewis and Debenhams.

“On balance we think that the power has swung back in favour of shoppers this year and we expect record online purchases over the next few days,” said Keith Richardson, managing director of the retail sector at Lloyds Bank Commercial Banking.

Black Friday comes amid mixed signals from the high street. This week the Multiyork Furniture chain called in administrators, while on Thursday Mothercare issued a profit warning that wiped nearly 20% off the value of its shares.

Yet the CBI’s monthly survey of retail activity suggested high-street sales had staged a recovery in November, despite the steepest growth in selling prices in almost 25 years.

“Our high streets are not out of the woods,” said Rain Newton-Smith, chief economist at the CBI. “Ahead of the crucial run-up to Christmas, the weaker pound has pushed up prices and retailers are nervous about business conditions and are trimming their workforces.”

British households are facing the biggest squeeze on living standards since records began, according to the Resolution Foundation, amid rising inflation due to the pound’s weakness since the Brexit vote.

Many consumers struggling with shrinking disposable income will have held back on spending in September and October to buy not just Christmas presents but essentials. Household gadgets such as coffee machines and food mixers are expected to be big sellers alongside the toys, games consoles and Fitbits destined for under the Christmas tree, as Britons scour the internet for the best deals.

“Both retailers and consumers are more savvy about Black Friday than they were a few years ago,” added Richardson. “Stores know better than to give away massive discounts on items consumers were going to buy anyway … shoppers, meanwhile, are better at spotting the worthwhile deals.”

Mark Newton-Jones, head of Mothercare, said British shoppers had gone “quiet” in recent weeks; Mothercare had had a sharp drop in customer numbers and sales.

His comments came as the group fell deeper into the red, reporting a pre-tax loss of £16.8m for the six months to 7 October. The results were dragged down by weakness in the company’s international business despite it spending heavily to revive sales at its UK stores amid stiff competition.

Richard Hyman, an independent retail consultant, described Next’s decision to get involved in Black Friday as a big surprise given that discounting only increased pressure on retailers’ profit margins. “It has taken [Next] years of sitting on the sidelines to make up its mind to join the fray,” said Hyman “I suspect this is more to do with wanting to boost flagging sales than a sudden liking for the lemming-like melee that is Black Friday.”